Exotic diseases and pests of trees have caused continental-scale disturbances in forest ecosystems and industries, and their invasions are considered largely unpredictable. We tested the concept of preinvasion assessment of not yet invasive organisms, which enables empirical risk assessment of potential invasion and impact. Our example assesses fungi associated with Old World bark and ambrosia beetles and their potential to impact North American trees. We selected 55 Asian and European scolytine beetle species using host use, economic, and regulatory criteria. We isolated 111 of their most consistent fungal associates and tested their effect on four important southeastern American pine and oak species. Our test dataset found no highly virulent pathogens that should be classified as an imminent threat. Twenty-two fungal species were minor pathogens, which may require context-dependent response for their vectors at North American borders, while most of the tested fungi displayed no significant impact. Our results are significant in three ways; they ease the concerns over multiple overseas fungus vectors suspected of heightened potential risk, they provide a basis for the focus on the prevention of introduction and establishment of species that may be of consequence, and they demonstrate that preinvasion assessment, if scaled up, can support practical risk assessment of exotic pathogens.

CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences Mengla 666303 China

Department of Biology Lund University Lund Sweden

Department of Biology William and Mary Williamsburg 23185 U S A

Department of Mushroom Science and Forest Microbiology Forestry and Forest Products Research Institute Tsukuba 305 8687 Japan

Department of Pest Management Faculty of Natural Resources Prince of Songkla University Songkhla 90110 Thailand

Florida Museum of Natural History University of Florida Gainesville 32611 U S A

Forestry and Game Management Research Institute 156 04 Prague 5 Zbraslav Czech Republic

Fujian Province Key Laboratory of Plant Virology College of Plant Protection Fujian Agriculture and Forestry University Fuzhou 350002 China

Graduate School of Bioresources Mie University Tsu Japan

Institute of Microbiology Czech Academy of Sciences Prague Czech Republic

Institute of Zoology Chinese Academy of Sciences Beijing China

Key Laboratory of Forest Protection of National Forestry and Grassland Administration Research Institute of Forest Ecology Environment and Protection Chinese Academy of Forestry Beijing China

Mientrung Institute for Scientific Research VNMN and Graduate School of Science and Technology Vietnam Academy of Science and Technology Hue Vietnam

National Institute of Forest Science Seoul South Korea

Peckerwood Garden Conservation Foundation Hempstead 77445 U S A

Plant Protection Institute The Volcani Center Rishon LeZion Israel

School of Forest Fisheries and Geomatics Sciences University of Florida Gainesville 32611 U S A

School of Life Sciences Hubei University Wuhan China

Shanghai Academy of Landscape Architecture Science and Planning Shanghai Engineering Research Center of Landscaping on Challenging Urban Sites Shanghai China

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